Experimental validation of axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency

The axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequency capability have been proposed by adjusting the external electric resistance and the ratio of piezoelectric layer numbers between the actuator part and the sensor part, which have promising potential in designing the novel cymbal transducer for underwater sound projector and ultrasonic radiator applications. In the previous studies, the multilayer models were established to guide the design of the transducers with arbitrary layer number, and analyzed the dynamic characteristics theoretically. In this work, an experimental study is performed to validate the theoretical models and predictions. Piezoelectric rings with multiple concentric annular electrodes are designed to characterize the multilayer piezoelectric composite cylindrical transducers. The top surface of the piezoelectric rings is divided into two separate parts. One part is covered by multiple concentric annular electrodes, corresponding to the piezoelectric layers, and the other part is uncovered, corresponding to the elastic layers. Four prototypes are fabricated and each consists of four concentric annular electrodes. The impedance spectra are measured by the impedance analyzer to obtain the resonance and anti-resonance frequencies. Effects of two adjusting methods on the dynamic characteristics are evaluated experimentally. The experimental results basically coincide with the theoretical ones. This comprehensive experimental work assures the feasibility of using axially polarized multilayer piezoelectric composite cylindrical transducers with adjustable multifrequencies and confirms the benefit of the developed theoretical models for guiding the fabrication and optimization of this type of transducers.

Track Model with Nonlinear Elastic Characteristic of the Rubber Rail Pad

This paper presents a new basic nonlinear track model consisting of an infinite Euler-Bernoulli beam (rail) resting on continuous foundation with two elastic layers (rail pad and ballast bed) and intermediate inertial layer (sleepers). The two elastic layers have bilinear elastic characteristic obtained from the load-displacement characteristic of the rail pad and ballast. A time-varying load with two components - time-constant one and harmonic other, representing the wheel/rail contact force is considered as the track model input. Rail deflection due to the time-constant component of the load is obtained solving the nonlinear equations of the balance position. Subsequently, the structure of the nonhomogeneous foundation is determined. Dynamic rail response in terms of receptance due to the harmonic component of the load is calculated using the linearised track model with nonhomogeneous elastic characteristic. Influence of the time-constant component and the reflected waves due to the nonhomogeneous foundation are presented.

Parametric study of a novel magneto-electro-aeroelastic energy harvesting system

This paper investigates a parametric study on a novel type of flutter-based aeroelastic harvester by utilizing magneto-electro-elastic materials, which can be used as an alternative to piezoelectric materials in aeroelastic harvesters to enhance the output electric power. The considered model includes a deformable clamped beam attached to a rigid airfoil, covering with one or two magneto-electro-elastic layers. Connected electrodes to magneto-electro-elastic layers capture potential electric from the produced electric field. Furthermore, an extrinsic coil is wrapped around the vibrating beam to produce the magnetic-based electric energy in the applied magneto-electro-elastic layer. First, the harvesting system is modeled as a discrete model to derive the governing equations using Faraday and Gauss laws, and the constitutive equations of magneto-electro-elastic materials according to Hamilton's principle. Then, different configurations have been examined and compared. Afterward, the effect of various parameters on the chosen harvester characteristics is investigated through considering stability to determine the optimal parameters resulting in the highest electric power generation. Lastly, the efficiency of the magneto-electro-aeroelastic harvester is compared with a piezo-aeroelastic counterpart indicating the supremacy of the presented harvester.

Printing a Pacinian Corpuscle: Modeling and Performance

The Pacinian corpuscle is a highly sensitive mammalian sensor cell that exhibits a unique band-pass sensitivity to vibrations. The cell achieves this band-pass response through the use of 20 to 70 elastic layers entrapping layers of viscous fluid. This paper develops and explores a scalable mechanical model of the Pacinian corpuscle and uses the model to predict the response of synthetic corpuscles, which could be the basis for future vibration sensors. The −3dB point of the biological cell is accurately mimicked using the geometries and materials available with off-the-shelf 3D printers. The artificial corpuscles here are constructed using uncured photoresist within structures printed in a commercial stereolithography (SLA) 3D printer, allowing the creation of trapped fluid layers analogous to the biological cell. Multi-layer artificial Pacinian corpuscles are vibration tested over the range of 20–3000 Hz and the response is in good agreement with the model.

Die equipment and tool for manufacturing sandwich flat ring parts with composites

The results of designing die equipment and special tool through separate die operations for manufacturing sandwich flat ring parts with the middle base metal layer and periphery elastic layers with increased composite thickness are shown. Efficient geometrical dimensions and a tool shape ensuring qualitative manufacturing parts mentioned and extension of technological potentialities of separating operations for their manufacturing, in particular, for design options with the increased thickness of periphery elastic composite layers are optimized experimentally.

Methods for producing of outer metal and central elastic layers three-layer seals

The limit values for the thicknesses of the outer metal layers for three-layer seals are established for conventional blanking and punching. New methods for manufacturing of these seals with increased thickness of the outer metal layers are developed.

Validity of Winkler’s mattress model for thin elastomeric layers: beyond Poisson’s ratio

Winkler’s mattress model is often used as a simplified model to understand how a thin elastic layer, such as a coating, deforms when subject to a distributed normal load: the deformation of the layer is assumed proportional to the applied normal load. This simplicity means that the Winkler model has found a wide range of applications from soft matter to geophysics. However, in the limit of an incompressible elastic layer the model predicts infinite resistance to deformation, and hence breaks down. Since many of the thin layers used in applications are elastomeric, and hence close to incompressible, we consider the question of when the Winkler model is appropriate for such layers. We formally derive a model that interpolates between the Winkler and incompressible limits for thin elastic layers, and illustrate this model by detailed consideration of two example problems: the point-indentation of a coated elastomeric layer and self-sustained lift in soft elastohydrodynamic lubrication. We find that the applicability (or otherwise) of the Winkler model is not determined by the value of the Poisson ratio alone, but by a compressibility parameter that combines the Poisson ratio with a measure of the layer’s slenderness, which itself depends on the problem under consideration.